The invention refers to an apparatus for holding a log or roll of web material such as paper, for example, during cutting thereof along a plane perpendicular to the log axis.
More particularly, the invention refers to an apparatus including a plurality of clamping elements distributed in a circle around the log, which are able to be moved so as to clamp the log during the cutting thereof but which can be released so as to allow said log to move forward between cuts. At least one actuator causes the movement of said clamping elements. Connectors which connect the clamping elements to one another to provide a simultaneous movement are driven by said actuator.
An apparatus of this type is described, for example, in the U.S. Pat. No. 5,038,647.
In the paper converting industry, relatively long ( e.g. 3-4 meters) logs or rolls of reeled paper material are frequently produced. Upon completion of the reeling, the logs are cut along planes perpendicular to their axes for the production of small rolls (e.g. 10-12 cm) of all-purpose wipers, toilet paper or similar products. The cutting of the log is accomplished by means of a log-saw provided with a suitable cutting tool which, in case of logs of limited diameters (e.g. 10-20 cm) is a rotating disk. In case of logs of larger diameters, it has been suggested (see for example the above-mentioned U.S. Pat. No. 5,038,647) the use of a band saw or similar cutting-off machine. In any case, the log is held, during the cut, in the regions adjacent to the cutting plane, both upstream and downstream of said region. The cited U.S. Pat. No. 5,038,647 describes a special clamping device which comprises radially movable slide members for circumferentially clamping the log during the cutting operation and releasing it to allow for its axial advancement between cuts. The movement, in radial direction, of the slides is obtained by a ring in which guide slots inclined with respect to the radial direction are formed, with journals which are fixed to the respective slides being able to slide within said guide slots. The rotation of the ring about its own centre causes a centripetal and centrifugal radial movement of the slides.
This holding device of known type, although extremely effective and reliable, exhibits some drawbacks due both to the complexity of the mechanical members used, and to the rigidity of the system which is suitable only for logs whose diameters vary within a somewhat limited range.